The present invention relates to a support frame for mounting and demounting electrical units, and more particularly to a frame for interchangeable electrical units of the type which are wired to a source of electrical current at one side thereof and are provided with actuating means, such as switches, at an opposite side thereof.
Frames of known design exhibit safety hazards and require extra-operational steps for mounting and demounting the units. The prior art frames as well as the cover plates which are mounted over the frames for aesthetic purposes are constructed of metal. If during the mounting process, a wire carrying electrical current becomes disengaged from its terminal post and touches the metallic frame and/or the metallic cover plate, a serious electrocution hazard would result for a worker or a user.
Another disadvantage of the prior art metallic frames is that an extra-operational step, i.e. the bending of a metallic tab, is required for fixed mounting of the electrical unit. After the electrical unit has been inserted into a respective slot, a nearby tab is provided so that it can be bent to wedge the unit in place. A worker installing a unit must pause to pick up a tool for bending the tab, then bend the tab, and finally replace the tool. The high cost of electrical work and the cost of the special tooling makes these time consuming tasks very costly when it is considered that many thousands of electrical units must be mounted in complex electrical installations, such as in the wiring of a building.
Furthermore, the prior art metallic construction does not allow for easy removal of the electrical units. Demounting requires rebending the tab back into its original position. This is an even lengthier and costlier operation as compared with mounting in view of the fact that more exactness is required in achieving the original orientation of the tab and the increased probability that the tab will break off and thereby make the frame worthless.
Prior art metallic frames are also not made of one-piece construction. If stiffening members are to be provided, they are added on at a later assembly stage. In other words, additional work and tooling is required to provide for a sturdy structure.